Pleistocene extinction of megafauna not caused by paleo-indian hunters

I've often been fascinated by the megafauna of the Pleistocene, more so than any other great epoch in history. I think the reason it interest me so much is because it was not all that long ago, and that modern humans interacted and hunted these animals. In France, beautiful cave drawings were painted by skilled ancient artist in Chauvet Cave over 25,000 years ago, depicting some animals than have since gone extinct. Around 13,000 years ago, the megafauna of the late Pleistocene began to disappear. The major extinciton happened in North America, however many megafauna on other continents also became extinct. Animals that went extinct included mammoths, mastedons, giant armadillo, giant beaver, giant bears, several species of wild horse, wooly rhino, species of bison and oxen, stag-moose and many others. Is it really plausible that the first people to arrive in the americas killed millions of animals to extinction? These were a nomadic people, living in small hunter groups, not organized communities or tribes of hundreds or thousands. We know that numbers of early americans were limited because the lack of archeological sites doesn't support large numbers of paleo-indians circa 13,000 BCE. Let us ask ourselves, how many people could one mammoth support and for how long? Around 490 lbs of meat can be extracted from a 1200 lb steer. A Columbian Mammoth weighed up to 10 tons or 20,000 pounds. So conservatively it may have yielded 5,000 to 7,000 lbs of meat! Through salting or smoking the meat can be preserved, as well as preserved naturally in colder conditions. It would have greatly benefited these hunters to find ways of preserving their kill, as hunts were undoubtedly dangerous and may not have always been succesful. The large number of predators at the time would surely have had a greater impact on reducing the numbers of grazing fauna. These predators include dire wolves, north american lions, bears, saber-toothed cats, and others. So what really happened?

Jul 4 2013:
When you say "not caused by", that sounds like we're looking for a single cause, but that's unlikely to have been the case. Since the end of the Pleistocene (like the end of all geologic periods) was a time of significant climate change, which means changes in sea level, in precipitation patterns, and in vegetation (and therefore also in the animals living off the vegetation - along with their predators), it's quite certain that these changes had an impact on the distribution and numbers of animals. The changes would also have affected the survival of many species: the end of each geologic period is also associated with an elevated rate of extinction.

The presence of a new predator - humans - was a new factor in the Americas, and would likely have had some impact on some animal populations. Locally, this may have been an important impact in some areas. There may also have been one or more catastrophic events. It seems like we don't yet know enough to assign weight to the various factors that brought about the end of much of the megafauna.

Careful scientists rarely say they "believe" that "this caused that" in historical studies. Rather, they think in terms of likelihood of various causes and interactions, and are prepared to modify their ideas as new evidence is found. So the best approach to the debate question is not to choose a side or make categorical statements, but to appreciate the complexity of it and to be informed by new information that becomes available.

Jun 19 2013:
Australia also had marsupial mega fauna. 90% of the large mammals became extinct coinciding with human migration.

In new Zealand giant flightless birds evolved due to a lack of mammalian predictors. Then the Maoris arrived. But there could be other factors related to human arrival and the reduction in large herbavores e.g. changes in vegetation density, the impact of man made fires etc

Climate change is a usual suspect, but I'm not in this case

We seem to see a similar pattern with the arrival of humans elsewhere.

As to the extinction of the large preditors I suggest it may simply be humans hunted their primary food sources

Jun 15 2013:
Your question about the advisability of preserving meat seems immaterial, we are unlikely to ever know since all the 13,000 year old jerky has been "hunted to extinction" through consumption or decay. The rest of your query seems analogous to the current debate over climate change or global warming. Many hard to measure factors all possibly contributing to a single result. For the climate argument it seems silly to discount human contribution since there really can be a tipping point where even an other wise negligible factor "might" be the straw that could tip the scale, overheat the planet and contribute to our extinction as a species. If it is possible to switch to renewable sources of energy (a desirable goal in itself, unless you are EXXON) why not do it. As Tom Toles recently asked in an editorial cartoon "what if we make a better world for nothing?"(supposing we really are not contributing to global warming).
For the American mega fauna it is much simpler it seems to me. Did humans eat two or more of each of these now extinct species? Apparently they may well have. Supposing those two were of both genders and contemporary to each other and nubile but had not reproduced. If we had not eaten them they MIGHT have had a large posterity and thus not gone extinct. So it appears certain to me we are guilty unless you can show that a comet or other natural disaster did in the residue of each population so completely that adding in any amount of potentially uneaten population would have made no difference to the outcome.

Jun 15 2013:
I don't think we have to prove that meat was being preserved to propose the idea. As is often the case in pre-history, there are many questions that remain unanswered. One theory seems to gain popularity and then is written as truth, although many questions remain. Any who question or challenge the accepted are chastised and ridiculed, some even lose their careers. I believe that there are simply too many different animal species that went extinct during that period to place blame on human expansion. The fact that it happened over almost every continent also raises questions. History does reveal that we are in an interglacial period, and that we are at the apex of that warming. CO2 levels are the highest that they've been in at least 800,000 years, at 390ppm compared to the 280ppm that it should be at this point in the interglacial. I don't think that is significant enough to prevent our planet's cooling. The fact is that CO2 levels have actually been higher for much of our earth's history, and as you would expect, temps were higher as well. Still, life flourished. I believe that we should strive to keep our planet as free from human influence as possible. However, people need to understand how dynamic the earth's climate is. The climate will change, history reveals that is a fact. It's how we react and deal with that change, that is the question.

Jun 12 2013:
Or how about the comet impact in the Great Lakes region about 12K years ago. It rerouted the Great Lakes out flow from the once more expansive Mississippi to the St' Lawrence, creating Niagara Falls. Surely that would have global implications. Mankind took a big hit from that and had it not happened we might be thousands of years ahead in terms of civilization.

Jun 19 2013:
Evidence of advanced middle eastern cities dating to around that time have been found--6 to 7 thousand years earlier than thought the progression. It is certainly possible that a comet impact in the Americas could impact the global climate and perhaps bring civilization-retarding events like sustained droughts or harsh weather and storms.

Jun 19 2013:
I was meaning to say that the areas in which civilisation as we know it first started are far away from north America. (mainly fron North Africa over to East Asia) Even if a comet impact in North America was noticeable in the Middle East, the effects would have only been decades not thousands of years.

Jun 19 2013:
I don't know how you could say that, Peter. A civilization could be killed off entirely by any number of events. See Göbekli Tepe, an ancient site in Turkey, which was advanced thousands of years ahead of what we thought were the beginnings of engineered cities. Ancient people capable of this were still not a massive population as lives today and lived precariously at the whims of nature--including comets if not volcanism anywhere else in the world. Humanity was almost stopped entirely about 75K years ago with the last eruption of a "super-volcano". It was in Indonesia and humans are thought to have been reduced to a few thousand survivors world wide--most being thousands of miles away. Anything that kicks up that much gunk into the atmosphere--a phenomenal cataclysm will bring on hardship if not destruction for early civilizations. Without the setbacks of Mt. Toba and perhaps the comet in the Great Lakes the story of humanity would be entirely different and we'd have a lot more ancient mitochondrial DNA lines existing in latter-day folks. Imagine being 75,000 years further advanced.

Jun 19 2013:
Did more than that. It extinguished all lines of mitochondrial DNA except the few that made it. There is no way to say if some of those strains might have been actually more advanced than the ones that just happened to survive. Conversley, they could be lesser or the same. No one knows how many people died as a result but it's not a stretch to say some human populations were wiped out entirely. Until then it had been a multi-million year march. Then the ELE event hit. And super-volcanoes are still active.

Jun 8 2013:
About 15, 000 years ago the earth was entering an interglacial period. There were several periods of warming and cooling for the next 5,000 years, ending with the younger dryas, which was a period of extreme cooling that lasted 1,000 years. There is some good evidence that suggest a comet impact over North America caused the younger dryas and extinction. The younger dryas also marked the end of the Clovis culture, which was replaced by the Folsom culture.

Jun 7 2013:
We have the same discussion in Australia. We had diprotodons and giant wombats and other giant marsupials. My theory is that they weren't hunted to extinction but harrassed to extinction. If you live in a small tribe of hunter gatherers, a herd of massive herbivores would be dangerous to hunt, and eat all the vegetation. If you kill the odd one and generally harrass them they might move on allowing smaller more manageable prey animals to move in. Constant harrassment and relocation would interupt the breeding of the large animals. It might have been just enough to push the balance over to gradual extinction.

Jun 8 2013:
Very possible. I often think of where humans originated, Africa, where humans have hunted and existed for 200,000 years. The megafauna such as elephants, rhinoceros, hippos, and giraffe have not disappeared, and humans have been there the longest.

Jun 6 2013:
It has recently been discovered that the people living in the North American area drove herds of bison over cliffs and the ones that survived were also killed, to prevent them from staying away from the area & informing other bison. How true this is is unknown. When we think of that time period, we usually think of vast herds of animals & huge amounts of predators, and that may not have been the case. There were also ice advances and maybe even droughts that brought on deaths, as happens in today's world.

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